use std::{fs, io, path, pin};

pub fn open_file(path: &path::Path) -> io::Result<Option<fs::File>> {
    match fs::File::open(path) {
        Ok(file) => Ok(Some(file)),
        Err(err) => match err.kind() {
            io::ErrorKind::NotFound => Ok(None),
            _ => Err(err),
        },
    }
}

#[derive(thiserror::Error, Debug)]
pub enum ParseFileError<ParseError> {
    #[error("io error: {0}")]
    IO(io::Error),

    #[error("parse error")]
    FromStr(ParseError),
}

pub fn parse_file<T: std::str::FromStr>(
    path: &path::Path,
) -> Result<Option<T>, ParseFileError<T::Err>> {
    match fs::read_to_string(path) {
        Ok(s) => Ok(Some(s.parse().map_err(ParseFileError::FromStr)?)),
        Err(err) => match err.kind() {
            io::ErrorKind::NotFound => Ok(None),
            _ => Err(ParseFileError::IO(err)),
        },
    }
}

pub type BoxByteStream = futures::stream::BoxStream<'static, io::Result<bytes::Bytes>>;

pub type BoxFuture<'a, O> = pin::Pin<Box<dyn futures::Future<Output = O> + Send + 'a>>;